Replaced BackgroundAnimator with ShelfBackgroundAnimator.

ash/shelf/shelf_view.cc

Index: ash/shelf/shelf_view.cc
diff --git a/ash/shelf/shelf_view.cc b/ash/shelf/shelf_view.cc
index 7ca66f899f82331e54b2a0a6019718f54886a4f1..be56dd489c6452490ccb8456b5032945e8a6aea4 100644
--- a/ash/shelf/shelf_view.cc
+++ b/ash/shelf/shelf_view.cc
@@ -14,6 +14,7 @@
 #include "ash/common/shelf/overflow_bubble.h"
 #include "ash/common/shelf/overflow_bubble_view.h"
 #include "ash/common/shelf/overflow_button.h"
+#include "ash/common/shelf/shelf_background_animator.h"
 #include "ash/common/shelf/shelf_constants.h"
 #include "ash/common/shelf/shelf_delegate.h"
 #include "ash/common/shelf/shelf_menu_model.h"
@@ -360,7 +361,8 @@ const int ShelfView::kMinimumDragDistance = 8;
 ShelfView::ShelfView(ShelfModel* model,
                      ShelfDelegate* delegate,
                      WmShelf* wm_shelf,
-                     Shelf* shelf)
+                     Shelf* shelf,
+                     ShelfBackgroundAnimator* background_animator)
     : model_(model),
       delegate_(delegate),
       wm_shelf_(wm_shelf),
@@ -388,7 +390,8 @@ ShelfView::ShelfView(ShelfModel* model,
       main_shelf_(nullptr),
       dragged_off_from_overflow_to_shelf_(false),
       is_repost_event_on_same_item_(false),
-      last_pressed_index_(-1) {
+      last_pressed_index_(-1),
+      background_animator_(background_animator) {
   DCHECK(model_);
   DCHECK(delegate_);
   DCHECK(wm_shelf_);
@@ -401,6 +404,8 @@ ShelfView::ShelfView(ShelfModel* model,
 ShelfView::~ShelfView() {
   bounds_animator_->RemoveObserver(this);
   model_->RemoveObserver(this);
+  if (background_animator_)
+    background_animator_->RemoveObserver(this);
 }
 
 void ShelfView::Init() {
@@ -418,6 +423,9 @@ void ShelfView::Init() {
   ConfigureChildView(overflow_button_);
   AddChildView(overflow_button_);
 
+  if (background_animator_)
+    background_animator_->AddObserver(this);
+
   // We'll layout when our bounds change.
 }
 
@@ -1370,7 +1378,7 @@ void ShelfView::ToggleOverflowBubble() {
     overflow_bubble_.reset(new OverflowBubble(wm_shelf_));
 
   ShelfView* overflow_view =
-      new ShelfView(model_, delegate_, wm_shelf_, shelf_);
+      new ShelfView(model_, delegate_, wm_shelf_, shelf_, nullptr);
   overflow_view->overflow_mode_ = true;
   overflow_view->Init();
   overflow_view->set_owner_overflow_bubble(overflow_bubble_.get());
@@ -1547,6 +1555,11 @@ void ShelfView::OnGestureEvent(ui::GestureEvent* event) {
     event->StopPropagation();
 }
 
+void ShelfView::UpdateShelfItemBackground(int alpha) {
+  GetAppListButton()->SetBackgroundAlpha(alpha);
+  overflow_button_->SetBackgroundAlpha(alpha);
+}
+
 void ShelfView::ShelfItemAdded(int model_index) {
   {
     base::AutoReset<bool> cancelling_drag(&cancelling_drag_model_changed_,